A wide range of medical procedures involve placing objects, such as sensors, tubes, catheters, dispensing devices, and implants, within the body. Position sensing systems have been developed for tracking such objects. For example, U.S. Pat. No. 5,983,126, to Wittkampf, whose disclosure is incorporated herein by reference, describes a system in which catheter position is detected using electrical impedance methods. U.S. Patent Application Publications 2006/0173251, to Govari et al., and 2007/0038078, to Osadchy, describe methods for sensing the position of a probe by passing electrical currents through the body between an electrode on the probe and a plurality of locations on a surface of the body. These methods likewise use the electrical impedance of the body in sensing probe position.
When using impedance-based measurement technology for determining the position of a probe (e.g., a catheter), it has been found that if the probe image is not constrained to assume realistic shapes and positions, sudden fluctuations can occur, which are disconcerting to the physician who is viewing the patient monitor. U.S. Patent Application Publication 2008/0009711, whose disclosure is incorporated herein by reference, describes methods for enhanced visualization of a probe when such measurement technologies are used by stabilizing a displayed image of the probe.